MacRumors published a story that Apple has released the third beta of tvOS 17 to registered developers.
Apple Seeds Third Beta of tvOS 17 to Developers
Apple today seeded the third beta of an upcoming tvOS 17 beta to developers for testing purposes, with the update coming two weeks after Apple introduced the second beta.
Registered developers are able to download the tvOS 17 update by opting in to the beta through the Settings app on the Apple TV. A registered developer account is required.